I am buying a Powermatic 66 Table saw. 3 hp 220v single phase.
I’m actually planning on making a 12ga extention cord about 25′ long and plugging it in as needed to the dryer outlet.
I’ll preface the next part with saying I’m a finish carpenter who has done many remodels and wiring along the way. I’ve added many extra breakers and circuits over the years and know how to figure out if the panel can handle another draw. I’m overly cautious. I know the mechanics of electrical but am not familiar with 4 wire 220 and how it should be run.
Now…Guy says it’s 3 wire 220v (2 hot 1 ground) and I have that type of dryer outlet. I need to spend today preparing the circuit. With my luck it’ll be 4 wire for which my home is not wired. I’ll need to make my 3 wire 220v outlet 4 wire.
Is this an easy task for someone of my abilty to figure out? The existing 3 wire 220 circuit is in conduit about 15 feet from the panel. It would be very easy to add another wire in there ( I don’t think it would over load the space-what can I fill 65% of the conduit with wire correct?)
Owner says he’s used a plug in the past but others say I should hard wire it. I’d turn the dryer outlet into a j-box if this is a 100% must do. This is not as convenient as now I’ll have a 12ga wire going across my rather small shop. I prefer to be able to plug in as needed.
Anything else I should know?
Thanks,
Notrix
Replies
The 240V motor is almost certainly 3-wire (two hots and a ground, no neutral). The only reason that a neutral might be needed is if the device contains some other equipment (eg, light, digital controls, etc) that would need 120V.
The only thing you probably need to do is to change out the existing 240V breaker for a smaller one, so that you're better protected against motor overloads, etc, and so your extension can be "legal". There's a special formula for motor circuits, though -- you need a slightly larger breaker than for a resistive load of the same nameplate amp rating, IIRC. If/when you change the breaker, it's probably a good idea to change the outlet similarly -- there are different outlet designs for the different current ratings.
If you want/need to convert to 4 wire, then pulling a neutral of the same size as the other wires is all you should need to do. It may be best to pull out the other wires and then pull them all back in together, though.
A large number of issues here.
99% sure that the TS is 240v OLNY, that is 2 hot and a GROUND. But in a some case people also run a neutral so that they can power a 120v feeder.
If the dryer connection is older 3 wire style it is does not have an EQUIPMENT GROUNDING CONDUCTOR ("ground), but a 240/120 circuit with 2 hots and a NEUTRAL and no ground.
In some cases it is a technicality if a ground or neutral is used for the 3rd wire, but in others it is very important.
But you already have a ground in that it is run in conduit.
There are a number of other issues here.
Another one is that existing circuit will probably have 30 amp breakers. That will require either #10 wire or changing to 20 amp breaker.
Also you need a disconnect someplace to remove power when working on the saw. That has to be within site of the saw. It can be a disconnect switch, a plug and receptacle or the CB if it is insight.
http://www.networkcable.com/pages/components/nema_nonlocking.html
If you have an old style dryer it will have ####10-30R receptacle with 2 hots and a neutral.
The 4-wire style will be a 14-30R (2 hots, neutral and ground).
The saw will use typically use ####6-20 or 6-30 (2 hots and a ground). but you could use a 14 series and not connect the neutral.
Now do you still want to use this with the dryer?
And what about extending the circuit to some place closer to where you will have the TS and then use a 10ft cord on the TS?
And does the TS already have any kind of cord or plug on it?
Also look at the wiring to the existing receptacle and tell me what there is?
Edited 1/15/2005 12:10 pm ET by Bill Hartmann
Edited 1/15/2005 12:32 pm ET by Bill Hartmann
You sure thats UNGROUNDED and not a bonded ground/neutral?
I will edit to make it clearer.
Yes, that is the "grounded conductor" (neutral), but not the Equipment grounding conductor (ground).But the code does make it clear that the 3rd connection is a neutral and not a ground.
Thanks, "Also you need a disconnect someplace to remove power when working on the saw. That has to be within site of the saw. It can be a disconnect switch, a plug and receptacle or the CB if it is insight." Not sure what you mean by this. The saw would be the only major draw in the house when on. Do you mean "when NOT working on the saw"?
You were correct in guessing/knowing it's a 10-30R. I've also been able to confirm it's 3 wire. With about 20 feet from outlet to saw the short answer seems to be 10ga cord correct?I'm a bit confused about the ground though. On this panel the neutral bar and ground are basically connected.... a matter of sematics or..??? Should I make sure it's connected to the ground buss instead of the neutral even though..??Also I've posted as well on Knots forum expecting to find more practical answers there ie those doing this same thing, and it seems common practice to do just this-plug into dryer outlet as is.Thanks again,
N
By working on the TS I did not mean work with.Rather actually working on the saw, manly changing blades.The "switch" (or starter) on the front is not to be trusted. Too easy to hit the on and some designs can activate with a hard jolt to the TS.So the 3rd wire is white wire that goes back to the panel?Yes, it is a technicality in this case, but not in all cases whether a this a "ground" or "neutal" as it goes back to the same place.But in sub-panel installation they are isolated.The best thing to do would be to run a ground wire back to the panel and install a 6-30 receptacle since you have conduit. But you can also pickup the ground from the box since you have metal conduit.Then tape off the white wire. More important then "meeting code" is that it makes it clear what that receptacle is used for and if anyone in the future goes to change it back to a dryer or do anyohter work there is less head scratching.
First, let's look at the circuit breaker requirements for the saw. A 3hp, 220/240V, single phase motor will have a full load current rating of about 17 amps. The way I size the breaker is to multiply the full load rating by 125% and then use the next size larger breaker. 17 amps x 125% = 21.25 amps, so I'd use a 25 or 30 amp breaker (25 would be best, but the 30 is probably easier to find at the hardware store, and it's still small enough to be allowable by the electrical code for this application.)
What size is the existing breaker in the panel for the dryer outlet? If it's 30 amps now it can be re-used, but I suppose (depending on what size dryer was plugged in it before) that it could be a 40 amp; if so you'll want to put in a smaller one. I assume you don't have an electric dryer anymore, so this circuit is just sitting there.
As Bill said earlier, it's about 99% sure that the saw needs three wires - the two hots and the ground, no neutral. Chances are the dryer outlet is wired with two hots and a neutral, with no ground, so that would have to be changed back in the panel (I assume this is the main panel for the house, and not a subanel.) You could probably move the neutral wire in the panel but I'd feel better about pulling a new ground wire so it's done right. Since it's in a short conduit that shouldn't be hard to do.
The receptacle should be changed to the proper style, which is a NEMA 6-30, or a NEMA L6-30 if you want to use a twistlock. Get a matching plug for the saw cord while you're at the store. Then, the power cord to the saw needs to be 2 conductor w/ground, #10 gauge.
What Bill was talking about as far as the disconnect is that there needs to be a way to disconnect power within sight of the saw. Assuming you can't see the breaker panel from where the saw is sitting, you either need a local disconnect switch (if the saw is hardwired) or a plug and receptacle where you can see it from the saw.
The 25' cord length shouldn't be a problem if you're concerned about voltage drop, probably the only issue would be if it's a tripping hazard. All things being equal it would be nice to have it shorter, so if you can extend the conduit and mount the receptacle closer to the saw it wouldn't be a bad idea.
You can see a handy chart of all the differnt plug and receptacle configurations at http://www.hubbellnet.com/max_htm/tech_stuff/NEMA/front.html.
An excellent explanation, If possible would you give a simple rundown on the ground/neutral. So many don't understand the use of either/ or. As I understand The theory is that the neutral is return with in the structure and as such is protected with jacket. and the ground(exposed) is redundant serving the same function, but not to be return load carrying primary. So when we look at the neutral/ground bonding at the panel, the protected circuit the neutral is upstream of the panel. And in newer separate ground/neutral the bonding does not take place upstream of the meter base/service entrance.
Am I close?
Here's a short explanation from the popularmechanics.com website.
The purpose of a separate grounding wire in a circuit is safety. This wire does not carry current during normal operation. Instead, it connects to ground components such as metal outlet boxes in which receptacles and switches are installed, metal appliance cabinets, and frames of motors. Although the ground wire does not normally carry a current, it will carry current in case an electrical short develops. In this case, the grounding wire directs the current safely to ground rather than shocking the person touching the appliance.
The neutral wire, although grounded, is not needed for safety. It carries current and is needed to close the electrical circuit. This allows the current in a branch circuit to flow from the electrical service panel through the appliance and back to the grounding bar in the service panel.
A more detailed discussion of the subject can be found on Mike Holt's website at http://www.mikeholt.com/mojonewsarchive/GB-HTML/HTML/Neutral-to-GroundConnections~20020521.htm
The easiest way to deal with this problem is to send the saw to me and buy one already wired the way you want. <G>